How to check if serial or parallel is crystal ?

[Moss]

Quartz Question

In the PIC 16 datasheet is mentioned that it must be used with quartz with parallel resonanse. How can I distinguish serial or parallel is crystal ? Is there general marking for parallel and serial resonance crystals ( for example all parallel mark with P and all serial with S,somethig like that.. )

 

[flatulent]

both resonances exist

All crystals have a series and a parallel resonant frequency that are very close together. (The difference is measured in parts per million.) Unless you are doing some very precise timing, it makes no functional difference if the frequency stamped on the case is the series or parallel resonant frequency. If you buy a crystal intended for uP clocks, it will probably be labeled for the parallel frequency.